1. Field of the Invention
This invention relates to improvements in an airbag restraint system, and more particularly to a structure of an airbag to be inflated under the action of gas generated from a gas generator.
2. Description of the Prior Art
It is well known that many automotive vehicles are equipped with an airbag restraint system to protect a passenger from impact during a vehicle collision. Such an airbag restraint system is disclosed, for example, in Japanese Patent Publication No. 56-43890 and Japanese Utility Model Provisional Publication No. 61-185642.
An example of such an airbag restraint system will be discussed with reference to FIGS. 5 and 6 of the present application. The airbag restraint system includes an airbag 1 which is supplied with gas to be inflated. The airbag 1 includes an installation section 2 which is formed with a gas inlet 5 through which a gas from a gas generator is supplied. A bag-shaped section 3 is sewed to the outer peripheral portion of the installation section 2. The installation section 2 of the airbag 1 is fixed to a base plate which is secured to a vehicle stationary side such as an instrument panel or a steering wheel. The gas generator is fixed to the base plate and adapted to be operated under a predetermined condition thereby to momentarily generate gas to be ejected into the airbag 1 so that the airbag 1 is instantly inflated.
During such an operation of the airbag restraint system, a high load is unavoidably applied to the installation section 2, so that there is a possibility of causing accidents such as the installation section 2 being disconnected from the base plate and/or being broken. In this regard, it has been proposed to form the installation section by piling up and sewing four sheet materials 6, 7, 8 and 9 together.
However, difficulties have been encountered in such a conventional airbag installation section 2 which is formed as follows: The four sheet materials 6, 7, 8 and 9 are formed separately. Then, the four sheet materials 6, 7, 8 and 9 are piled up and sewed together. Finally, a bag-shaped section 3 is sewed to the installation section 2. Thus, many sewing steps are required, in which sewing operation of the bag-shaped section 3 to the installation section 2 is particularly troublesome. This degrades the operational efficiency of producing the airbag and in assembling the airbag restraint system. Additionally, a plurality of sheet materials 6, 7, 8 and 9 are required thereby increasing the number of constituent parts.